I saw a discussion on another list and I'm posting a reply here because it may be of interest to our readers, and it is OT (off topic) on the other list. Someone said they wanted to make their own plate reverb.

I made one once. It worked great. I saw a letter to the editor of an electronics experimenters magazine. I'll pass my experience along here.

I got a sheet of steel, about the size of a very large refrigerator, this was about 1 X 2 meters more or less. I built a wooden frame of 2X4s. Two holes were drilled near the top of the plate and it was suspended to hang on two wooden dowels through rubber grommets.

I took an old 12" speaker and cut the metal cage off of it and trimmed the speaker cone so as to only have about 1" from the driver. Then I built a wooden cross member across the plate but not touching it to hold this speaker and glued the shortened cone to the plate. I attached a contact microphone to the plate. I drove the plate through a 50 watt amplifier connected to the speaker (glued to the plate) and took the signal from the contact mic. The placement of the mic is determined by experimentation. I built a simple wet/dry mixer. In those days people built their own circuits. Today I'd buy the mixer.

This entire apparatus was in the basement below my studio.

This is similar in design to a spring reverb, but uses the plate instead.

Digital reverbs can emulate the sound of these devices pretty well, except when you overdrive a plate or spring you get great effects that can't be easily modeled. When I moved from California to Pennsylvania, I left the plate reverb hanging in place. I took the mixer and power amp with me. I miss that reverb because of the organic sound it made while being overdriven. I still have a spring reverb. I use it with the Moog modular, or used to. Electro/mechanical reverbs have lots of hum and noise.

One thing that might be of interest. There is a legend that in the 1930's in New York a major radio studio bought an abandoned subway tunnel and made a reverb unit out of it by placing powerful speakers at one end and a microphone at the other.

Back in the 6o's and early 70's, people made experimental "reverb" devices with plastic tubes. The flexible accordion type tubes, like dryer vent tubes, worked very well.

I'd be interested if anyone else has some thoughts or experience to share about electro/mechanical reverbs and the like._________________--Howard
my music and other stuff

This is an excellent article. My home grown plate reverb was much simpler, using wooden construction. I suspect the one described in the above article is over built. Consider that if you want something that sounds like an old expensive plate reverb, use a cheap digital reverb. I have an old Midiverb III that is fine for this purpose. If you want something that sounds really unique, build your own and don't focus on trying to recreate something else. Using the driver described in this article is a big improvement over using a butchered speaker I used, not because it will sound better, but because it is so much easier to build._________________--Howard
my music and other stuff

A place that has added speakers & mics to a grain mill (the LARGE kind), and allows users to upload sounds to play through it:

Quote:

Sounds arrive inside Silo #5 by telephone or internet. They are then broadcast into the vast concrete grain storage chambers inside the Silo. They are transformed, reverberated, and coloured by the remarkable acoustics of the structure, yielding a stunningly beautiful echo. This sound is captured by microphones and rebroadcast back to its sender, to other listeners and to a sound installation outside the building. Anyone may contribute material of their own, filling the instrument with increasingly varied sounds.

By the way -- I have taken audio samples & made impulse responses from a US Titan Missle Silo that was long abandoned. I'll have to dig those up if I remember to do it

I'd be interested if anyone else has some thoughts or experience to share about electro/mechanical reverbs and the like.

When I was a mere sprout I used a garden hose coiled in a box with something like a 5” speaker driving a funnel stuck into the hose on the outside. There was a mike in a small box at the other end of the hose inside the larger box and the larger box was filled with sand. I got this design out of oneof the popular DIY magazines of the time—early sixties.

I don't remember how it sounded--probably rather awful--but at the time...._________________The question is not whether they can talk or reason, but whether they can suffer. -- Jeremy Bentham

Bachus, the first reverb I ever used was the spring reverb you built for the Jacksonville University electronic music studio in 1967. It was excellent. You could overdrive it and it would literally scream with delight and horror._________________--Howard
my music and other stuff

Bachus, the first reverb I ever used was the spring reverb you built for the Jacksonville University electronic music studio in 1967. It was excellent. You could overdrive it and it would literally scream with delight and horror.

Thanks for the complement. Those spring units were a great improvment over garden hoses. Of course all I built was the electronics._________________The question is not whether they can talk or reason, but whether they can suffer. -- Jeremy Bentham

My name is James, currently studying for a degree in Music Technology in London, England. I am in the process of building a plate reverb for part of my own project for my course. I have made the frame and the sheet metal is attached. I am now in the middle of putting together the tricky part of using the speakers etc. At the moment I have a 5w speaker, and i have managed to attach a couple of 9v batteries to it, which appears to be making the speaker work, as it pops up and down when I put the battery on. The part I'm having trouble with, is that I am using a Piezo Transducer contact microphones to record the input sound and then through and out of the speaker. I appear to not be getting any sound out of the my speaker when I tap the transducer. (I am attaching the transducer cables directly to the speaker). I do not know of any other way to fix this problem. I was wondering if you were able to help me at all. I cannot find any help online at all. I found you through your this website,

OK, James. I choose to answer this on the public forum because it might be of interest to more people. I hope you join the forum.

Mounting the speaker is the hardest part because you have to support the heavy part - the magnet - in such a way the the cone can move freely. The cone is glued to the plate.

Connect an audio amplifier to the speaker. That's what you drive the plate with. The piezo transducers are for the pickup. The speaker and the transducer are completely independent, except that they are both attached to the plate. I found it best to attach the speaker to a point near the center of the plate, and the transducer somewhere near one of the edges.

I've got a driver which I think could work really well for this. It's from a special seat cover designed to shake your seat for video games. It's a bit like a normal speaker driver, but instead of a cone, it has a suspension plate made of fibreglass. The coil is firmly attached to the back of the fibre glass, and the middle of the suspended part has a bolt through it, so you can attach it to the thing you want to shake. I think the coil is rated at about 50W.

Now,.... to find something big to shake! _________________What makes a space ours, is what we put there, and what we do there.

Thankyou for the reply howard! That was helpful. I do have a couple more questions.

Part of my dissertation project is that I am going to be giving new life to old discarded items. So for instance, and old drinking glass. I will be attaching a piezo transducer to the glass and smashing it on the ground and creating music from this. My plan was to do this by smashing it, projecting the audio through the plate and then recording the outcome. Do you think it would be better if I smashed the item, recorded it first, then played it out from the file saved on my laptop and then recorded the reverb out come? I hope that makes sense! Also can you suggest any good audio amplifiers?

Part of my dissertation project is that I am going to be giving new life to old discarded items. So for instance, and old drinking glass. I will be attaching a piezo transducer to the glass and smashing it on the ground and creating music from this. My plan was to do this by smashing it, projecting the audio through the plate and then recording the outcome. Do you think it would be better if I smashed the item, recorded it first, then played it out from the file saved on my laptop and then recorded the reverb out come? I hope that makes sense! Also can you suggest any good audio amplifiers?

First, to electro-music.com

Smashing the glass with a transducer connected to it is a great idea! Please post a recording of this when you get something, and be careful.

I would certainly record without reverb or any other processing. Then apply reverb or other effects.

As for good audio amplifiers. For the plate reverb, you really don't need anything really good. I'd go for some used PA amp of about 25 to 50 watts power output. Mono is what you need. I'd check out a pawn shop or some used gear or second-hand type store.

As for good stereo amps for listening - this is my opinion and other's will disagree: Amplifiers have been commodities since the mid 1970s. They are all very good now, even stuff you get from discount electronics places will blow away very expensive amps from earlier decades. They are now very inexpensive too. IMHO, the most important thing is the connectors on the back for the speaker wires; that is the primary point of failure on amps. Get something that has very good connectors, preferably something that uses banana jacks. If it doesn't have banana jacks, I would avoid it. If it does, it's probably a pretty good amp.

I recently picked up a great 5.1 amp from Best Buy - the store brand. Very cheap - great connectors - sounds great.

I prefer monitors that have built-in amplifiers. My favorite brand is JBL. Again, just my opinion - but I'm right. _________________--Howard
my music and other stuff

This may not be the best place for these questions, but as it has to do with the construction of my plate reverb so it might be useful for others with this same situation:

So I have been clearing out my dad's old warehouse with the goal of transforming it to a nice, big studio space. There is a lot of old junk, though, so I have come across tons of material to put together some fun toys. In particular, of course, I'm putting together this reverb using a large metal shelf and an old security alarm horn.

Which brings me to my first question: is there a practical way of determining how hard I can push the horn? It is a solid metal horn with no useful info printed anywhere on it, but I image it can take a lot - it was, after all, originally used in an alarm system which was very, very loud. It has no low-end to speak of, but this isn't a problem since I would normally use a high pass or something before sending the signal to the reverb so this just saves a step. It is worth noting that the cable going into the horn seems something like 14-18 gauge - so maybe this can help me find a reasonable limit. (The last thing I need is a fire in my studio, though I don't think I would ever push it as hard as it could probably go.)

My second question has to do with grounding the mics coming back to the board. I'm not worried about grounding the signal going into the horn since the whole set-up is so lo-fi, but the distance back to my board will be enough to worry about interference. Especially considering all the other equipment and lights, etc in between. The mics have an ungrounded 1/4" jack, but how can I make sure the signal (from the jacks to the board) is grounded? The frame supporting the plate is an old metal bed frame, so could I just solder the "ground" part of a spliced XLR to the frame somewhere and then connect the "+/-" to a regular 1/4" tip as usual?

This is a perfect situation to use a direct box, which converts the unbalanced mic signal into a balanced signal. Balanced lines are much more resistant to picking up common-mode noise._________________--Howard
my music and other stuff

That had occurred to me, and in fact my summing mixer, which will return the four contact mics as well as a few room and overhead mics back to the main console, is balanced. So I could put it close to the plate, but I would prefer not to have to walk downstairs & back to make volume or panning adjustments, etc. Also, the other mics & preamps are already wired to go back to the console, so that is just not the best option.

I have been thinking about this (obviously), and I wonder if there might be another way which doesn't require using four DIs. You see, I need to repair the lead for the amp head pushing the plate speakers anyway - someone wisely pulled out the ground part of the power cable. Might it be possible to tap into the ground for the amp to balance the mics?

The ground is meant to dissipate static electricity (i.e. noise), so it seems to me that I should be able to get the job done with this method. Also, if I were to use DIs, they would basically be sharing the same ground as the amp head since they would be using the same set of outlets.

(Yes, I know, it does sound rather lazy & cheap... but I could use those DIs elsewhere, and I really don't want to have to walk all over the place for something that can be easily done from the comfort of my nice Captain Kirk chair.)

Conventional wisdom is that you use balanced lines for mics, and for long runs of line level signals. In your situation, I would not want to run up and down stairs trying to get a creative solution to work.

Power supply grounds are a completely separate problem. Power grounds almost never get rid of noise, they are a source of noise. I know of studios where all of the power supply grounds are bypassed on every piece of audio and computer equipment. This is a trick roadies have known for over 50 years, at least the audio part.

You've got at least 6 mic lines to return. You might consider getting an 8 channel direct box. That will be a good bang for the buck._________________--Howard
my music and other stuff

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